Rotor control



Feb. 16, 1950 SHA@ w. YUAN ET AL 2,925,129

ROTOR CONTROL 6 Sheets-Sheet l Filed April 26, 1957 Feb. 16, 1960 sHAo w. YUAN ETAL 2,925,129

ROTOR CONTROL Filel April 2e, 1957 6 Sheets-Sheet 2 INVENTORS Q/iao h/e/ )faQ/z, /260032/2? /0/2 //a ATTORNEY Feb. 16, 1960 y sHAo w. YUAN ErAL 2,925,129

' RoToR CONTROL Filed April 2e, 1957 e sheets-sheet s Y 1 INVENTORS @a Jia@ fifa/2 Yacvz.

eaw'e //a/7 /faW/df? ATTORNEY Feb. 16, 1960 sHAo w. YUAN ETAL 2,925,129

ROTOR CONTROL 6 Sheets-Sheet 4 Filed April 26. 1957 INVENTORS' a@ da@ i//ff/Z Yea/2. /Zea/:f l/a/I /fa ATTORNEY 6 Sheets-Sheet 5 INVENTORS web ATTORNEY Feb. 16, 1960 sHAc w. YUAN ETAL RoToR CONTROL Filed April 26, 1957 Feb 16, 1960 sHAo w. YUAN ETAL A 2,925,129

ROTOR CONTROL Filed April 26, 1957 6 Sheets-Sheet 6 ATTORNEY Figure is another form of cyclic control for variably supplying the control jets to activate the jet means in the leading or trailing edge of the rotor blade to provide: greater lift force in the reverse. flow region;

Figure 11 is a perspective View of a rotary blade havin jet ducts in both the leading and the trailingedge; and Figure 12 is still another embodiment of jet vcontrol means in a trailing edge with at leastV two elongated vspans of jets.

neath the airfoil near or substantially at the trailing .edge 19.. The air foils have a central spar and beams 21.and ,22 over lwhich the airfoil skin 23, see Figure 4, is formed in anV oval shaped arrangement for the most desirous airfoil circulation. A pattern of the desired air flow for lift with zero incidence is illustrated in Figure 2. In order to have a substantially close vapproach to this high life flow pattern, the present trailing under edge jet controls are provided, so as to obtain the flow pattern of Figure 3, which is very close to the desired flow pattern of Figure 2.

The novel features of an airfoil, which is oval in cross section with a rounded leading edge and a rounded trailing edge combined with the novel effects ofa. jet

In Figure 4 one detail of a jet structure is illustrated, for example, 24 is a jet nozzle formed with an exterior threaded reduced portion 25, which threads into the wall of a threaded opening in the ltube 17 and is limited and locked in position by an internally threaded washer 26.

The discharge end of the jet nozzle 24 may have an outwardly flared bore and is formed with an annular flange 27 adapted to provide a flush fit of the nozzle tip with the exterior of the airfoil skin surface 23.

The center spar 20, see Figure 5, is formed with a yflattened lug-like end 28 bored through to provide for connection by rivets or bolts 29 and 30, see YFigure 1 to the diametrically opposite radial bifurcated arms 31 and 32 of a mounting bracket 33 pivotally mounted on the hollow rotor post 34 by pin 35.

The jet tubes 17 are sealed off at the blade tips and are coupled by suitable fluid-tight coupling nuts 36 andV 37 to fluid supply conduits 38 and 39, respectively.

YThese conduits lead from coupling means 40 and 41,

stream placed along the rear calculated dividing streamline corresponding to a predetermined calculation may be defined and emphasized as by the following example:

Consider a circular cylinder moving through `a stationary fluid. lf the potential flow is calculated about a circular cylinder corresponding to an arbitrary circulation, the two symmetrical dividing streamlines are known, and a lift coefficient of 41r(CL12.6) is obtained, if the two stagnation points have come into coincidence at the bottom point of the cylinder. The general effect of the circulation is to increase the relative speed of the fluid at the surface above the stagnation points of the cylinder, and to diminish the speed at the surface below. Thus the pressure above the stagnation points is diminshed .and the pressure below is increased, and therefore there will be an upward force on the cylinder in the direction perpendicular tothe flow direction. If a thin flap of certain short length or a jet stream be placed along the rear calculated dividing stream line corresponding to certain circulation, approximately the same lift would be produced on the cylinder.

Similarly the above theory holds true for an oval shaped airfoil instead of a cylinder, however, the magnitude of the lift coeflicient is somewhat smaller depending on its thickness ratio. The means used to produce a very high lift on an airfoil of oval shape and the like by placing a thin flap or a jet stream at the calculated dividing streamline is called the circulation control airfoil.

The disclosure in the present application has suggested the use of a rotor blade having -a cross-section shape which resembles an elongated oval with a blowing jet of fluid capable `of being adjustably displaced with respect to the blade so as to attain the desired high lift.

In this device, see Fig. 3 in the application, the air stream can flow upon the upper side of the blade around its rounded trailing edge, instead of the sharp trailing edge in the conventional blades, and smoothly off the rounded trailing edge with the jetstrearn where the circulation is created. Hence, a considerable increase in lift coefficient can be accomplished without the necessity of the change of the blade pitch angle. Thus, the present invention uses the principle of circulation control to pro duce high lift and to alternate lift force during flight respectively, from valve chambers 42 and 43 diametrically extended from each side of the hollow rotor post 34. Butterfly valves 44 and 45 are mounted in the valve chambers 42 and 43, respectively, and the cyclically l controlled by a Vswash plate 46 adapted to be tilted by a pilot control link 47 with a yoke 48 connected by cross pin 49' to a sleeve 50 operatively connected to the balljoint portion 51 of the swash plate Y46. The annular surface of the plate 46 is engaged by follower rollers 52 and 53 carried by roller shafts 54 and 55 connected by link members 56 and 57, respectively, to each respective butterfly valve 44 and 4S. Each roller is shock Vmounted in a bracket 58 and 59rby springs` 60 and 61 engaged at oneend with the underside of the said brackets and each spring resting at the other end on the roller forks 62 and 63, respectively.

The jet means inv the blades or airfoils 15 and 16 are supplied with -air or gas from a suitable source-in the fuselage by supply hose 64, which connects by coupler nut 65 to the hollow rotor post 34.

If the swash plate 46 is in level position the respective butterfly valves 44 and 45 will be in a position parallel to the air or lgas flow, that is, wide open. This position of the valves provides the hovering condition of the rotary craft, a helicopter, for example, as all the blades give equal lift force. This is because the momentum of the blowing jets of all blades are equal.

If the pilot desires to descend or ascend vertically, he

can decrease or increase the Iblowing quantity of the air or gas by adjusting the power plant, not shown, which is producing the jet power. Then for forward or sidewise flight and control due to gust, the pilot by rod 47 can tilt the swash plate 46 to any desired direction. The rods 54 and 55 are thus displaced, which in turn regulates the butterfly valves 44 and 45 cyclically. This gives the desired amount of uid flow to the respective jet pipes in each blade 15 and 16 at any given azimuth position.

Figure 6 is a modification of the jet arrangement, wherein jets 18 are spaced and skewed from a low point X to a slightly higher level Y along the lenfth of a jet tube 17.

Another modification of the jet arrangements is illustrated in Figure 7, wherein Athe jets 18 are made progressively smaller from the root of the blade where the velocity is least to tip of the blade where the velocity is greatest, or vice versa in order to for the rotor.

While in Figure 7 there is disclosed'a multiplicity of relatively closely spaced jet orices, such orifices if increased to an infinite number would result in a slot 18a as indicated -in Figure 7-A, which is capable of optional circulation.

This slot 18a may be ofgradually decreased width from one end thereof to correspond with the structure of Figure 7 or the same may be of uniform f width throughout its length. Y

noem as Still another modification of the jet system is illustrated `n1 Figures 8 and 9; wherein the swash plate 46', hollow rotor post 34 a'nd airfoil construction are substantially the same as in Figure 1. However, the lift distribution may be collectively controlled to adjust the net lift of the rotor by providing an operator link 70 manually operated by the pilot and connected to the bifurcated lug 71 of a` crank arm 72 fixed on an extension 73 of a jet pipe 74. This pipe 74 is mounted to turn in bearing means 7 5 carried by supporting bracket 76. Thus the jet directions may be collectively adjusted to hover conditions, offorward thrust and for ascending and descending. i The jetdlr'ections may alsoibe cyclically control-ledby tilting the swash plate 46' when the link 70 is connected to the sv'vash plate.

The swash plate 46' may be tilted to control therdirec tion of the jet fluid by a butterflyvalve 77 at the root of" each jet pipe, see Figure 9. This operation is identical to that described f or Figure 1.

`Another form f this invention is disclosed in' Figures 10 and `1 1 and provides for directing air or gas to jet means 8@ and 81 located underneath the airfoil 82 at both edges of the same.

vThe control for this arrangement includes diametrically positioned buttery valves 84and 85 and a pair ofliuid, that is, air or gas diverter valvesV 83 and 86' positioned iii rvalve chambers 84d and 86a on each side of a hollow rotor post 87. These' chambers are supplied with the `jet duid through openings 87a and Sf7b leading7thereto-from the interior'of'the post 87 connectedto aV supply source. valves 83 and 86 are controlled by a cam plate 88 and cam 89 for twopositions of valves 83 and 86. The cani plate is `formed with a depending annular collar ,90 s lidably and tur'nably mounted around an upwardly formed annuular bearing collar 91H carried by a caniV plate support 92 fixed to the aircraft frame. The diverter valves 83 and 36 each are controlled by crank arms 93 and 94, respectively, which pivotally connect to the free ends of vcam follower rods 95 and`96, respectively, each being" formed with a roller forlc 97 and a roller 9S journalled therein on an axle pin 99. The cam 89 has two` positions, that is upper and lower positions,` corrtiolled by a lug i)EL from a control link, not shown. Forfexainple, at low dightspeeds the'lower cam position is'inactive and suitable iiuid, such as air or gas may be continuously supplied throughthe openings S7a and 9,7b o f`post'l87 and the valvesto the trailing edge jet pipe 81, and at" high iiight speeds the upper cam position is aetiveV and cyclicallydiver'tsair to'the leading edge by the diverter valves S3 and Se, seel Figure' l0.

The butterliyvalves 84 and $5 are identicalto `those o f lriigureA l and are controlled by a s wash plate `100, which `is tilted bya pilotcontrol rod 101, yoke 102 and hallijoint' arrangement 103 through follower rods 104 and 105 to each of the respective buttery valves to control the` guantityof the air or gas supplied to the airfoil jets. These 4follower rods are each biased into Contact with their respective cam'surfaces and swash plate surfaces by coil springs 106, 107, 198 and 109.

lso," another arrangementof jet angles may be provided by Figure 12, wherein jets 11i) and 111 are providedrin the trailing edge 112 of airfoil 113. With this aringementair is directed to either jet chamber 114 or ,tra to ontrol high speed byY jets 110 or a low'speed and hovering condition by jets 111.

Thus a novel rotor system is provided that utilizes rotor yblades with circulation controlled by means of jets located beneath the airfoil near the trailing edge. As. explained airfoil circulation determines the lift which is measured by a lift coefficient, designated CL Hence,` the blade CL can be directly controlled by means of the jets. The control of CL in a conventional airfoil must be effected by a change in incidence of the airfoil, since the angle of the conventional sharp trailing edge pri- 6 marily'controls the CL.' 'llhus it is disclosed and illu'strated that theCL in the proposed rotor, thereforeycan be varied by varying any one or a combination of the following:

( l) Airfoil incidence (as with a conventional airfoil).

(2) let location.

'(3) Jet discharge angle.

(I4) let velocity or mass flow (jet momentum).

The advantages of this type of jet control for an airfoil applied to a helicopter rotor, for example, are as follows:

(l) The rear stagnation point location is not dependent on a sharp trailing edge as in a conventional airfo'il. This means that the airfoil need not have a sharp trailing edge. This should decrease structural problems.. However, a sharp trailing edge may be retained for other reasons.

(2) Mechanical complexity can be greatly decreased, since the airfoil can be mounted with a fixed Vangle of incidence, Vthe CL being controlled by the jets.

(3) Since the CL can be increased without a high angle f `blade incidence, boundary layer separation problems are minimized and lhigh CL values (five or larger) Can be realized. This will allow the design of amuch more favorable spanwise CL distribution than is now practical,

(4) `The jet is inherently directed so that one component of the jet thrust aids the rotor rotation. Therefore, the po-wentransmitted through the rotor shaft for rotation can be reduced or entirely eliminated by proper `jet design.

While only several specific embodiments are hereinbefore illustrated and described, it is to be expressly understood that this invention is not intended to be limited to the exact formations, construction or arrangement of parts as illustrated and described because various modi iications may be' developed in putting the invention to practice within the'scope of the appended claims.

What We claim is:

l. An airfoil oval shape in cross section for rotary `wing aircraft having a rounded leading edge and a round-ed trailing edge, and jetstream producing means in at least one of saidedges, disposed along the underportion of the airfoil at the calculated dividing streamlines thereby controlling the circulation and increasing the `co etiicient of lift.

2. The structure according to claim 1 `wherein `said means is angularly adjustable to vary thel direction of the jets for controlling circulation of a` resulting air stream .around the airfoil.

3. The structure according to claim 1 wherein said jet producing means comprises an elongated tube disposed lengthwise of the airfoil, `and jet openings in the wall of said tube in spaced relation lengthwise thereof,

4. The structure according to claim 1 wherein said jet producing means comprises an elongated tube disposed lengthwise of the airfoil, and a jet opening in the wall of said tube in the form of an elongated slot..

5. The structure according to claim 4, wherein said slot is defined by walls converging from :adjacent one end of the tube to the other end thereof.

6. The structure according toY claim 3 wherein said openings are disposed in angular relation to the chord of the blade.

7. The structure according to claim 3, wherein said openings are of varying size from one end of the tube toward the other end.

8. The structure according to claim 3, wherein said airfoil comprises a central longitudinally disposed spar sand a longitudinally disposed beam between said spar `and each edge of the airfoil, an airfoil skin supported on said spar and said seams, and said tube being disposed between one of said beams and the adjacent edge of the airfoil adjacent said skin, thereof.

9. The structure according to claim 8 wherein said zles whose outer ends are engaged with said skin and whose inner endsrare threaded into topped openings in 410. A rotary wing aircraft comprising a hollow post, means for supplying air under pressure through the post, hollow oval airfoil means having an inner post adjacent portion and a tip mounted for rotating on said post, an air conveying conduit extending from the post to said blade means at the root portion thereof, jet tubes mounted in the airfoil means and extending spanwise Aand along theV trailing edge thereof, means connecting the conduits to the jet tubes, said jet tubes having jet nozzles therein opening. into the air stream below said trailing edge, said jet nozzles being -angularly positioned to induce a desired circulation pattern around the airfoil adapted to greatly improve the coetiicient of lift thereof during the retreating movement of the blade means during rotation of the same.

1l. The structure according to claim 10, together with means for cyclically controlling the supply of air to said jet tubes with respect to the said retreating movement of the said blades.

12. The structure according to cla-im 10, wherein a bracket is pivotally supported on said post,vsaid air foil means being connected to said bracket.

13. A rotary wing air craft comprising a hollow post, a bracket pivotally connected to said post, a pair of air foils ofoval cross section form having adjacent ends l thereof connected to said bracket, a tube in each of said airfoils adjacent one edge thereof, jet nozzles in said tubes opening through said airfoils,'a pair of air or gas cham- ,bers disposed at`diametrically opposite positions on on said post, means for supplying air or gas to said chambers, conduits disposed between said chambers and said tubes for providing theV latter with jet forming gas, a normally opening butterfly control valve in each chamber and means supported by said post for cyclically operating said valves for unequal distribution of air or gas to said tubes in synchronism with the forward and retreating movement of said airfoils during rotation. Y

14. The structure according to claim 13, wherein said last-named means comprises a swash plate, means for rocking said plate, and means dishposed between said plate and said Ivalves for operating the latter in conformity with the movement of said plate.

15. A rotary wing air craft comprising a hollow post, a bracket pivotally connected to said post, a pair of airfoils of oval cross sectional form having adjacent ends thereof connected to said bracket, a tube in each of said airfoils adjacent one oval edge thereof, jet nozzles in said tubes opening through said airfoils, a pair of gas charnbers disposed at diametrically opposite positions on said post, means for supplying gas to said chambers, conduits disposed between said chambers and said tubes for pro- Ividmg the latter with jet forming gas, a normally open- 'ing butterfly control valve in eachV chamber and means supported by said post for cyclically operating said'valves for unequal distribution of gas to said tubes in synchronism with the forward and retreating movement of said airfoils during rotation, a second nozzle provided tube ,',within each airfoil adjacent the opposite edge thereof, a diverter valve in each of said chambers, and cam means yfor operating said diverter valves, for selective admission of gas toy one or the other of said tubes.

i' .16. rotary wing air craft comprising a hollow post,

a bracket pivotally connected to said post, a pair of airfoils of oval cross sectional form having adjacent ends thereof connected to said bracket, a tubepin each of said `airfoils adjacent one oval edge thereof, jet'nozzles in said tubes opening through said airfoils, a pair of gas chambers disposed at diametrically opposite positions on said post, means for supplying gas to said chambers, conduits disposed between said chambers and said tubes for providing the latter with jet forming gas, a normally opening butterlly control valve in each chamber and means supported by said post for cyclically operating said valves for unequal distribution of gas to said tubes; in synchronism with the forward and retreating movement of said airfoils during rotation, and means for rotating said tubes on their axis for varying the anguarlity of said jet nozzles.

17. A rotary wing aircraft comprising a post, va pair of airfoils of generally oval cross sectional form, means connecting adjacent ends of said airfoils to said post, a tube disposed within each airfoil adjacent an edge thereof, jet nozzles in said tubes opening through said airfoils, and means for admitting gas to said tubes, said tubes being supported Vwithin said airfoils for rotation about their axis and means for rotating the tubes for variable angular disposition of the nozzles therein.

18. The structure according to claim 17, together with means for selectively varying the mass of air or gas W admitted to the tubes.

19. A rotary wing aircraft comprising a'post, a pair of airfoils of generally oval cross sectional form, means vconnecting adjacent ends of said airfoils to said post, a tube disposed within each airfoil adjacent an edge thereof, jet nozzles in said tubes opening through said airfoils, and means for admitting gas to said tubes, a second nozzle provided tube within each airfoil adjacent the opposite edge thereof, and means for varying the volumes of gas admitted to the two tubes in each airfoil.

20. In a rotary wing aircraft a pair of opposed air foils of generally oval cross sectional form in the provision of a leading rounded edge and a rounded trailing edge, a pair of adjacent gas chambers adjacent one rounded edge thereof, a series of jet openings in the rounded edges of said airfoils communicating with each of said chambers, and means for selectively admitting gas to said chambers.

21. A method of inducing circulation of air transverse an airfoil, which comprises providing a jet stream at the rear of the calculated dividing streamline tofutilize the vertical component of the jet stream to provide an approach to a maximum coei'licient of lift of the airfoil.

22. A method of inducing circulation of air transverse an airfoil which comprises providing a jet stream at the rear of the calculated dividing streamline to utilize the horizontal component of the jet stream to provide torque for the rotor rotation.

References Cited in the tile of this patent UNITED STATES PATENTS Lee Feb. 21, 1950 

